I will build a 4'x16' table whose top I would like to be as flat as I
can get it. I don't know how best to accomplish this. The top will be
two sheets of 3/4" Birch ply butted against each other along the short
I toyed around with the idea of building a torsion-box like structure
out of ordinary studs to support the top. I was not successful in
getting the tops of the cross members and of the aprons flush. Some
sanding might do the trick but I don't know how to go about that either.
By the way, the frame will be two 4'x8' frames put together as well.
Based on the answers I got from you guys, it seems that the flatness of
the top is a function of the frame itself. What do you suggest for the
frame in the way it is built? One suggestion that came through was 3"
solid aprons with cross members every foot.
Say I got the frame right. How would I then insure that the plywood top
is also flat? If the ply has any imperfections, I don't know how to get
it flat across such a large surface area. Or is this simply not a
consideration if the top of the frame is flat?
It will need to support about 600 lbs distributed roughly even across
its length and I don't want the top to sag in time. I am planning to
finish the top with some kind of plastic film like varnish.
Please forward any suggestions. I am not very experienced. Thanks for
taking the time to answer.
Good day all,
Joe Tylicki wrote:
Its not likely you'd get a very flat top that way. Studs are seldom very
straight to begin with, and if they are not already dry, they will probably
bow and twist as they equilibriate to the humidity in your workspace.
I'd stick with a torsion box, but made of plywood. You'll need a way to rip
the plywood into very straight runs about 3 inches wide (not trivial, but can
be done with a table saw and some care, or a "shooting board" with a circular
saw). And you 'll need a way to cross cut those strips at exactly 90 degrees.
If you can make those cuts, then run continuous pieces the long (8 ft.)
direction about a foot apart. Cut shorter pieces to join them on about 1 ft.
centers, forming a 1 ft. square grid. You can use biscuits or splines to join
the parts. When joining the parts, use clamps and small blocks of plywood
covered in clear packing tape to keep them in vertical alignment.
Ordinary studs are seldom straight. Consequently, they are a poor choice of
material from which to create something which is flat and square.
How flat is flat? The fame should take a care of sagging issues, but not
minor surface imperfections.
Crappy grades of plywood have more surface imperfections than good ones. Are
we talking about CDX or cabinet grade ply?
Once again, we need more data. How is the table to be used? Does it need
knee space? How many legs? How where will they me placed? If you want four
legs under the corners, your going to need a hell of alot more apron than 3
inches to support a 16' span.
Start with the 30,000 ft view, like "I want to build a platform to support
my model train set..."
Simple. Make it as flat as *you* can get it, or take it to someone
with bigger equipment. The high school I attended had a huge
blet-sander; that is, a suspended belt, and you ran a hand-held plate
back and forth pressing the belt onto the work. It's called learned
technique ...and having the right tools.
I guess I missed that. This has ot be a troll, because you have to be
kidding about butting together 2 pieces of plywood and looking for
serious comments on keeping it flat without an underlying support
CD (in lRNOf.10458$Sp2.757@fed1read02) said:
| Hey folks,
| I will build a 4'x16' table whose top I would like to be as flat as
| I can get it. I don't know how best to accomplish this. The top
| will be two sheets of 3/4" Birch ply butted against each other
| along the short sides.
A while back I built a 12' sign and had the same problem (there are a
couple of photos at the link below). I routed a pair of matching (to
+/- 0.0005") quarter-inch by three inch "steps" on the edges to be
joined and used Titebond glue with a full-width clamp. When dry, I
sanded lightly with 220 grit paper and it came out well.
Another option is to clamp the pieces together and to a good work
support and inlay a piece of 3/8" ply across the back of the joint.
If you aren't concerned about the look or feel of the back, you could
just glue a plywood strip of appropriate width across the back of the
DeSoto, Iowa USA
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